As image capturing devices for capturing an image by scanning a surface of an object using a one-dimensional imaging element having a plurality of light-sensitive pixels arrayed in a line shape, imaging sensors called contact image sensors (CISs) are known. Contact image sensors are widely used for image-capturing functions of, for example, copying machines, image scanners, facsimile machines, or the like. Contact image sensors of these types use an optical element called a rod lens array for forming an erect equal-magnification image, thus there is the problem that the depth of field is small. Therefore, a technique for improving the depth of field is disclosed in Patent Literature 1 (Japanese Patent Application Publication No. 1994-342131), for example.
A contact image sensor disclosed in Patent Literature 1 includes a plurality of lens elements as an optical element for forming an erect equal-magnification image. In order to improve the depth of field, an overlapping limiting member for limiting overlapping of optical images formed by the plurality of lens elements are provided on or near an emitting surface of each of the lens elements.